1. Field of the Invention
The present invention relates to a process for delignifying lignocellulosic pulps and, more particularly, to a process for accelerating or catalyzing the alkaline cooking of lignocellulosic pulps.
2. Description of the Prior Art
The major alkaline pulping processes for the manufacture of chemical pulps are the soda process, and the sulfate or kraft process. Over the years various modifications and improvements to these basic alkaline processes have been described in the patent and technical literature. These improvements have variously addressed themselves to increasing yield, abating pollution and increasing the rate and extent of delignification. In line with the foregoing, there have been a number of publications which have dealt with accelerating these alkaline pulping processes.
Remler, U.S. Pat. No. 2,068,151, discloses that the alkaline cooking of fibrous materials, such as straw, grass, corn stalks, bagasse and wood chips excluding resinous woods, can be materially shortened by the addition of a small amount of an introfier, for example, turpentine, aniline, or pyridine, to the alkaline cooking medium. More recently, Bach and Fiehn disclosed in East German Pat. No. 98,549 that the pulp yields obtainable from the soda process can be enhanced by the addition to the pulping liquor of small quantities of anthraquinone-2-monosulphonic acid. Most recently, in 1977, Holton disclosed, in U.S. Pat. No. 4,012,280, that the addition of anthraquinone, and certain of its derivatives, to a soda or a kraft cook serves to increase the yield and the rate of delignification, and when used in the soda process also maintains the system free of any objectionable sulfur compounds.